Question

The Rh factor was first discovered in
(a) Monkey
(b) Guinea pig
(c) Man
(d) Rabbit

Answer 1

Hint: mammalian closely resembles human beings that share nearly 93% of DNA with humans that are listed as threatened species by IUCN.

Complete answer:
Karl Landsteiner and Alexander S.Wiener first discovered the Rh factor in the red blood cells of rhesus monkeys(Macaca mulatta) in 1937.
The Rh blood system has about 49 different types of antigens. When we say a person is Rh positive or Rh negative we specifically refer to the D antigen i.e. Rh D positive or negative.

Additional Information: - The Rh factor depends on three pairs of alleles present on chromosome 1 according to Fisher and Race hypothesis.
- Rh antibodies play a significant role in blood transfusions.
- The Rh antibodies also play a significant role in the hemolytic disease of the fetus and newborn(HDFN).
- Rh D antibodies are generally absent in the blood. But if an Rh-negative person is exposed to an Rh-positive person then the antibodies are formed in the person with Rh-negative blood due to exposure to Rh antigen.
This concept mentioned above is the cause of hemolytic disease of the fetus and newborn (HDFN) also called Erythroblastosis foetalis. It occurs due to the genetic incompatibility between an Rh-negative mother and her Rh-positive fetus.
So, the correct answer is ‘monkey’.

Note: The Rh factor present on the surface of RBCs of the monkey is not actually exactly identical to the Rh factor present in humans. However, by the time this was discovered, the term Rhesus was already very widely used. Consequently, the term was left unchanged but is now more commonly known as the Rh factor.